As one of the largest breeds of domestic rabbit, the Flemish Giant is a semi-arch type rabbit with its back arch starting back of the shoulders and carrying through to the base of the tail giving a "mandolin" shape. The body of a Flemish Giant Rabbit is long and powerful with relatively broad hindquarters. Bucks have a broad, massive head in comparison to does. Does may have a large, full, evenly carried dewlap (the fold of skin under their chins). The fur of the Flemish Giant is known to be glossy and dense. When stroked from the hindquarters to the head, the fur will roll back to its original position. ARBA standard has seven different colors, black, blue, fawn, light gray, sandy, steel gray and white. They are shown in six classes (three buck classes and three doe classes): Junior bucks and does under 6 months, Intermediate bucks and does 6–8 months, and Senior bucks and does 8+ months. The minimum show weight for a Senior (older than 8 months) doe is 14 lbs (about 6.4 kg), and the minimum weight of a Senior buck is 13 lbs (about 5.9 kg) (ARBA Standards of Perfection). A senior doe can take 1 year to reach full maturity. A senior buck can take 1.5 years to reach full maturity. It is not unusual to see a 10 kilo (22 pound) Flemish Giant, with the largest weighing as much as 50 pounds; although these species technically constitute Continental and German Giants.
Flemish Giants can be fed like other rabbits, with the amount increased to match their larger size. ARBA recommendations include hay and occasional treats. In supplementing a commercial diet, care must be taken to avoid excess protein, calories, and minerals such as salt and calcium, which in excess can cause kidney stones. Overfeeding leading to obesity is a major health concern for both commercial and pet rabbits.
The House Rabbit Society recommends 2 cups of chopped leafy vegetables per 6 pounds (3 kg) of body weight and no more than 2 tablespoons of fruit or carrots per 6 pounds of body weight daily.